Parallel plate waveguide for power semiconductor package

ABSTRACT

A power semiconductor package includes a first group of semiconductor dies attached to a first side of a substrate and evenly distributed over a width of the substrate and a second group of semiconductor dies attached to the first side of the substrate and evenly distributed over the substrate width. Each die in the first and second groups has all terminals at one side which is attached to the first side of the substrate and an insulated or isolated face at a side opposite the side with the terminals. A first intermediary metal layer of the substrate forms a first DC terminal. A second intermediary metal layer of the substrate forms a second DC terminal. These intermediary metal layers are insulated from one another and form a parallel plate waveguide. Additional power semiconductor package embodiments are described.

TECHNICAL FIELD

The present application relates to power circuits, in particular powercircuits with low parasitic inductance.

BACKGROUND

Power semiconductor packages include power semiconductor dies such aspower transistor and/or power diode dies attached to a substrate such asa printed circuit board (PCB), laminate or ceramic substrate having apatterned metallized surface. The parasitic inductance in thecommutation circuits of a power semiconductor package ideally should beextremely low to allow fast switching of the power semiconductors. Thereis a need for such power semiconductor package designs with very lowparasitic inductance in the commutation circuits.

SUMMARY

According to a first embodiment of a power semiconductor package, thepower semiconductor package comprises a substrate, groups ofsemiconductor dies and DC terminals. The substrate comprises a lowermostmetal layer, an uppermost metal layer, a first intermediary metal layerseparated from the lowermost metal layer by a first insulating layer,and a second intermediary metal layer above and separated from the firstintermediary metal layer by a second insulating layer and below andseparated from the uppermost metal layer by a third insulating layer,the uppermost metal layer being pattered into a plurality of stripswhich extend in parallel over a width of the substrate. A first group ofsemiconductor dies is attached to a first one of the strips of theuppermost metal layer and evenly distributed over the width of the firststrip. A second group of semiconductor dies is attached to a second oneof the strips of the uppermost metal layer and evenly distributed overthe width of the second strip. A third group of semiconductor dies isattached to a third one of the strips of the uppermost metal layer andevenly distributed over the width of the third strip. A fourth group ofsemiconductor dies is attached to a fourth one of the strips of theuppermost metal layer and evenly distributed over the width of thefourth strip. A first DC terminal is attached to a fifth one of thestrips of the uppermost metal layer and evenly distributed over thewidth of the fifth strip. A second DC terminal is attached to a sixthone of the strips of the uppermost metal layer and evenly distributedover the width of the sixth strip. The first group of semiconductor diesis electrically connected in series to the second group of semiconductordies. The third group of semiconductor dies is electrically connected inseries to the fourth group of semiconductor dies. The first DC terminalis electrically connected to the first intermediary metal layer througha plurality of conductive vias that extend through the third and thesecond insulating layers and insulated from the second intermediarymetal layer. The second DC terminal is electrically connected to thesecond intermediary metal layer through a plurality of conductive viasthat extend through the third insulating layer.

According to a second embodiment of a power semiconductor package, thesubstrate comprises a lowermost metal layer, an uppermost metal layer,and at least a first insulating layer separating the lowermost metallayer from the uppermost metal layer, the uppermost metal layer beingpatterned into a plurality of strips which extend in parallel over awidth of the substrate. A first group of semiconductor dies is attachedto a first one of the strips of the uppermost metal layer and evenlydistributed over the width of the first strip, each semiconductor die inthe first group having an insulated or isolated face attached to thefirst strip. A second group of semiconductor dies is attached to thefirst strip of the uppermost metal layer and evenly distributed over thewidth of the first strip, each semiconductor die in the second grouphaving an insulated or isolated face attached to the first strip. Afirst DC terminal is attached to the first strip of the uppermost metallayer and evenly distributed over the width of the first strip. A secondDC terminal is attached to a second one of the strips of the uppermostmetal layer and evenly distributed over the width of the second strip.The first group of semiconductor dies is electrically connected inseries to the second group of semiconductor dies.

According to a third embodiment of a power semiconductor package, thesubstrate comprises a lowermost metal layer, an uppermost metal layer,at least a first insulating layer separating the lowermost metal layerfrom the uppermost metal layer, and an intermediary metal layerinsulated from the uppermost and the lowermost metal layers. A firstgroup of semiconductor dies is attached to a first side of theintermediary metal layer and evenly distributed over a width of theintermediary metal layer, each semiconductor die in the first grouphaving an insulated or isolated face attached to the first side of theintermediary metal layer. A second group of semiconductor dies isattached to a second side of the intermediary metal layer opposite thefirst side and evenly distributed over the width of the intermediarymetal layer, each semiconductor die in the second group having aninsulated or isolated face attached to the second side of theintermediary metal layer. The lowermost metal layer of the substrateforms a first DC terminal of the power semiconductor package, theuppermost metal layer of the substrate forms a second DC terminal of thepower semiconductor package, and the intermediary metal layer of thesubstrate forms an AC terminal of the power semiconductor package. Thefirst group of semiconductor dies is electrically connected in series tothe second group of semiconductor dies.

According to a fourth embodiment of a power semiconductor package, thesubstrate comprises a plurality of metal layers separated from oneanother by an insulating layer. A first group of semiconductor dies isattached to a first side of the substrate and evenly distributed over awidth of the substrate, each semiconductor die in the first group havingall terminals at one side which is attached to the first side of thesubstrate and an insulated or isolated face at a side opposite the sidewith the terminals. A second group of semiconductor dies is attached toa second side of the substrate opposite the first side and evenlydistributed over the width of the substrate, each semiconductor die inthe second group having all terminals at one side which is attached tothe second side of the substrate and an insulated or isolated face at aside opposite the side with the terminals. An uppermost one of the metallayers at the first side of the substrate is patterned to form a firstDC terminal of the power semiconductor package, and a lowermost one ofthe metal layers at the second side of the substrate is patterned toform a second DC terminal of the power semiconductor package. The firstgroup of semiconductor dies is electrically connected in series to thesecond group of semiconductor dies.

According to a fourth embodiment of a power semiconductor package, thesubstrate comprises a lowermost metal layer, an uppermost metal layer,and an intermediary metal layer separated from the lowermost metal layerby a first insulating layer and separated from the uppermost metal layerby a second insulating layer, the uppermost metal layer being patternedinto a plurality of strips which extend in parallel over a width of thesubstrate. A first group of semiconductor dies is attached to a firstone of the strips of the uppermost metal layer and evenly distributedover the width of the first strip, each semiconductor die in the firstgroup having an insulated or isolated face attached to the first strip.A second group of semiconductor dies is attached to the first strip ofthe uppermost metal layer and evenly distributed over the width of thefirst strip, each semiconductor die in the second group having aninsulated or isolated face attached to the first strip. A third group ofsemiconductor dies is attached to a second one of the strips of theuppermost metal layer and evenly distributed over the width of thesecond strip, each semiconductor die in the third group having aninsulated or isolated face attached to the second strip. A fourth groupof semiconductor dies is attached to the second strip of the uppermostmetal layer and evenly distributed over the width of the second strip,each semiconductor die in the fourth group having an insulated orisolated face attached to the second strip. The first group ofsemiconductor dies is electrically connected in series to the secondgroup of semiconductor dies, and the third group of semiconductor diesis electrically connected in series to the fourth group of semiconductordies.

According to a fifth embodiment of a power semiconductor package, thesubstrate comprises a plurality of metal layers separated from oneanother by an insulating layer. A first group of semiconductor dies isattached to a first side of the substrate and evenly distributed over awidth of the substrate, each semiconductor die in the first group havingall terminals at one side which is attached to the first side of thesubstrate and an insulated or isolated face at a side opposite the sidewith the terminals. A second group of semiconductor dies is attached tothe first side of the substrate and evenly distributed over the width ofthe substrate, each semiconductor die in the second group having allterminals at one side which is attached to the first side of thesubstrate and an insulated or isolated face at a side opposite the sidewith the terminals. A first intermediary one of the metal layers of thesubstrate forms a first DC terminal of the power semiconductor packageand a second intermediary one of the metal layers of the substrate formsa second DC terminal of the power semiconductor package. The first andthe second intermediary metal layers of the substrate are insulated fromone another and form a parallel plate waveguide.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The elements of the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding similarparts. The features of the various illustrated embodiments can becombined unless they exclude each other. Embodiments are depicted in thedrawings and are detailed in the description which follows.

FIG. 1A illustrates a sectional view of a first embodiment of a powersemiconductor package.

FIG. 1B illustrates a top down plan view of the substrate shown in FIG.1A.

FIGS. 2-9 illustrate sectional views of exemplary semiconductor dieconfigurations in which the die backside is insulated or isolated fromthe uppermost metal layer of a package substrate.

FIG. 10 illustrates a sectional view of a second embodiment of a powersemiconductor package.

FIG. 11 illustrates a sectional view of a third embodiment of a powersemiconductor package.

FIG. 12 illustrates a sectional view of a fourth embodiment of a powersemiconductor package.

FIG. 13 illustrates a sectional view of a fifth embodiment of a powersemiconductor package.

FIG. 14 illustrates a sectional view of a sixth embodiment of a powersemiconductor package.

FIG. 15 illustrates a sectional view of a seventh embodiment of a powersemiconductor package.

FIG. 16 illustrates a sectional view of an eighth embodiment of a powersemiconductor package.

FIG. 17 illustrates a sectional view of a ninth embodiment of a powersemiconductor package.

FIG. 18 illustrates a sectional view of a tenth embodiment of a powersemiconductor package.

FIG. 19 illustrates a sectional view of an eleventh embodiment of apower semiconductor package.

DETAILED DESCRIPTION

Embodiments described herein integrate a parallel plate waveguidestructure or an approximated parallel plate waveguide structure into thedesign of a power semiconductor package, e.g. for full integration of a3-phase inverter or a 3-level circuit. The parallel plate/approximatedparallel plate structures described herein are waveguides in thatelectric (E) and magnetic (B) fields enclosed by the plates areperpendicular to one another and shielded by the plates (skin effect).Current enters through one plate and exits through the other plate orapproximated plate. While there may be some disturbance e.g. due toconnections to DC− and/or DC+ terminals, the E and B fields stillalternate over the length of the parallel plate/approximated parallelplate structures.

In some embodiments, the top (uppermost) plate, which may include morethan one layer of the substrate, approximates a planar plate design andis formed by bond wire connections to the top metal layer of thesubstrate and to the power semiconductor dies, and the powersemiconductor dies themselves. In other embodiments, both plates areformed by metal layers of the substrate. In each case, individualisolation layers or barrier layers can be provided at the bottom side(collector/drain/semiconductor substrate or cathode/anode) of the powersemiconductor dies to yield a lateral structure with back sideisolation, simplifying the design of the parallel plate/approximatedparallel plate structure. Both the parallel plate waveguide structureand the approximated parallel plate waveguide structure significantlyreduce the parasitic inductance in the commutation circuits of the powersemiconductor package, allowing for faster switching of the powersemiconductor dies included in the package.

FIG. 1A illustrates a sectional view of a first embodiment of a powersemiconductor package. The power semiconductor package comprises asubstrate 100. FIG. 1B illustrates a top down plan view of the substrate100.

The substrate 100 includes a lowermost metal layer 102, an uppermostmetal layer 104, a lower intermediary metal layer 106 and an upperintermediary metal layer 108 above the lower intermediary metal layer106. The lower intermediary metal layer 106 is separated from thelowermost metal layer 102 by a first insulating layer 110. The upperintermediary metal layer 108 is separated from the lower intermediarymetal layer 106 by a second insulating layer 112, and separated from theuppermost metal layer 104 by a third insulating layer 114. The uppermostmetal layer 104 is patterned into a plurality of strips 104 a-104 jwhich extend in parallel over a width (W) of the substrate 100.

The power semiconductor package further comprises a first group 116 ofsemiconductor dies, a second group 118 of semiconductor dies, a thirdgroup 120 of semiconductor dies, a fourth group 122 of semiconductordies, a fifth group 124 of semiconductor dies, and a sixth group 126 ofsemiconductor dies. The first group 116 of semiconductor dies iselectrically connected in series to the second group 118 ofsemiconductor dies to form a first half bridge, the third group 120 ofsemiconductor dies is electrically connected in series to the fourthgroup 122 of semiconductor dies to form a second half bridge, and thefifth group 124 of semiconductor dies is electrically connected inseries to the sixth group 126 of semiconductor dies to form a third halfbridge to yield a 3-phase inverter. A generic circuit schematic of anexemplary 3-phase inverter is shown in FIG. 1A, where device Q1generically represents the first group 116 of semiconductor dies, deviceQ2 generically represents the second group 118 of semiconductor dies,etc. Each device Q1, Q2, . . . , Q6 shown in the circuit schematic isimplemented by a plurality of semiconductor dies attached in a row toone strip of the uppermost metal layer 104 of the substrate 100. Thesemiconductor dies can include power MOSFETs (metal-oxide-semiconductorfield effect transistors), IGBTs (insulated gate bipolar transistors,SiC or III-V power semiconductor transistors such as GaN transistors,etc. The transistor devices can be lateral or vertical devices.

To ensure current sharing of paralleled power semiconductors, each groupof semiconductor dies is attached to one strip of the uppermost metallayer 104 and evenly distributed over the width of that strip. As such,the semiconductor dies in each group are placed side-by-side in a singlerow and the rows of dies are attached to parallel ones of the metalstrips. The direction of each row of dies is oriented perpendicular tothe current flowing within the parallel plates of the waveguidestructure. The parallel plate waveguide structure comprises the upperand lower intermediary metal layers 106, 108 of the substrate 100.Current enters the upper intermediary metal layer 108 via a DC+ terminalof the package which is attached to one of the strips 104 h of theuppermost metal layer 104, and current exits through the lowerintermediary metal layer 106 via a DC− terminal attached to a differentstrip 104 g of the uppermost metal layer 104. The DC+ and DC− terminalsare evenly distributed over the width of the corresponding metal strips104 g, 104 h to ensure the current is spread relatively evenly acrossthe width of the substrate 100.

The DC− terminal is electrically connected to the lower intermediarymetal layer 106 of the substrate 100 through a plurality of conductivevias 128 that extend through the third and second insulating layers 114,112. The conductive vias 128 are insulated from the upper intermediarymetal layer 108. The DC+ terminal is electrically connected to the upperintermediary metal layer 108 of the substrate 100 through a plurality ofconductive vias 130 that extend through the third insulating layer 114.First additional conductive vias 132 extend through the substrate 100 toconnect the source (emitter) terminals of the low-side powersemiconductor dies represented by devices Q2, Q4 and Q6 in the schematicillustration to the DC− reference plane formed by the lower intermediarymetal layer 106. Second additional conductive vias 134 extend throughthe substrate 100 to connect the drain (collector) terminals of thehigh-side power semiconductor dies represented by devices Q1, Q3 and Q5in the schematic illustration to the DC+ reference plane formed by theupper intermediary metal layer 108. The conductive vias are illustratedas dashed circles in FIG. 1B since they are covered by the strips of theuppermost metal layer 104 in this view. The position of the intermediarymetal layers 106, 108 of the substrate 100 electrically connected to theDC+ and DC− terminals can be switched as would the correspondingconductive vias, to yield an alternative design with the same parallelplate waveguide features. Unbundling the DC power terminals and thelayers within the substrate 100 in the way illustrated in FIGS. 1A and1B yields a more robust parallel waveguide design with fewerdisturbances e.g. due to connections to DC− and DC+ terminals.

A first AC terminal AC1 is attached to the same strip 104 b of theuppermost metal layer 104 as the second group 118 of semiconductor diesand evenly distributed over the width of that strip 104 b. The source(emitter) of each semiconductor die included in the first group 116 ofsemiconductor dies is electrically connected to the metal strip 104 b towhich the first AC terminal AC1 is attached to form the first phase ofthe 3-phase inverter. A second AC terminal AC2 is attached to the samestrip 104 d of the uppermost metal layer 104 as the fourth group 122 ofsemiconductor dies and evenly distributed over the width of that strip104 d. The source (emitter) of each semiconductor die included in thethird group 120 of semiconductor dies is electrically connected to themetal strip 104 d to which the second AC terminal AC2 is attached toform the second phase of the 3-phase inverter. A third AC terminal AC3is attached to the same strip 104 f of the uppermost metal layer 104 asthe sixth group 126 of semiconductor dies and evenly distributed overthe width of that strip 104 f. The source (emitter) of eachsemiconductor die included in the fifth group 124 of semiconductor diesis electrically connected to the metal strip 104 f to which the third ACterminal AC3 is attached to form the third phase of the 3-phaseinverter. Each DC and AC terminal can be implemented as a separatebusbar or as a plurality of pins attached in a row and distributedevenly over the width of the corresponding metal strip of the uppermostmetal layer 104. The drain (collector) connections of the semiconductordies are through the bottom side of the respective dies to thecorresponding metal strip of the uppermost metal layer 104. The gateconnections are not shown for ease of illustration.

A DC-link capacitor (Clink) of the 3-phase inverter can also beintegrated into the package design as shown in FIGS. 1A and 1B. In oneembodiment, the DC link capacitor is implemented as a plurality ofcapacitor dies coupled in parallel between the DC+ and DC− planes. Thecapacitors are attached to and connect two strips 108 a, 108 b of theupper intermediary metal layer 108 of the substrate 102. These twostrips 108 a, 108 b of the second intermediary metal layer 108 extend inparallel over a width of the second intermediary metal layer 108. Thecapacitors are evenly distributed over the width of the secondintermediary metal layer 108 of the substrate 100 to even currentdistribution.

The substrate 100 to which the semiconductor dies of the 3-phaseinverter are attached can be any standard substrate having a pluralityof metal layers separated by insulating layers. For example, thesubstrate can be a laminate, a ceramic-based substrate such as a DCB(direct copper bonded) substrate, AMB (active metal brazed) substrate,or DAB (direct aluminum bonded) substrate with metallized surfaces, aprinted circuit board (PCB), a substrate produced by a chip embeddingtechnology such as eWLB (embedded wafer level ball grid array), etc.

The semiconductor package embodiment illustrated in FIGS. 1A and 1Butilizes semiconductor dies having an active backside i.e. verticaldevices in which current flows between the front side facing away fromthe substrate 100 to the backside attached to the substrate 100. Thesemiconductor package embodiments described next utilize semiconductordies having an insulated or isolated backside, simplifying the design ofthe parallel plate waveguide. Various die configurations arecontemplated which have an insulated/isolated backside. FIGS. 2-9illustrate various exemplary semiconductor die configurations in whichthe die backside is insulated or isolated from the uppermost metal layerof the package substrate.

FIG. 2 shows a vertical power transistor die such as a power MOSFET orIGBT in which current flows vertically through the active area 200 ofthe die between the source/emitter (S/E) and the drain/collector (D/C)of the die. The amount of current flow is controlled by the voltageapplied to the gate terminal (Gate) which is disposed at the front sideof the die. The source/emitter terminal also is disposed at the frontside. The drain/collector terminal is disposed at the backside of theactive area. An insulator 202 such as a dielectric or molding compoundcovering the bottom side of the drain/collector terminal or a pnjunction ensures proper electrical isolation between the drain/collectorterminal of the die and the uppermost metal layer of the packagesubstrate. The drain/collector terminal is brought up to the front sideof the die so that all electrical connections are made at this side ofthe die. A termination/passivation layer 203 is provided at the frontside of the die to ensure proper isolation of the die terminals.

FIG. 3 shows a lateral power transistor die such as a GaN HEMT (highelectron mobility transistor) in which current flows laterally throughthe active area 204 of the die between the source/emitter anddrain/collector of the device. All terminals of the lateral die areformed at the front side of the die i.e. the side of the die facing awayfrom the package substrate. An insulator 206 such as a dielectric ormolding compound covering the bottom side of the die active area or a pnjunction ensures proper electrical isolation between the die and theuppermost metal layer of the package substrate. Atermination/passivation layer 207 is provided at the front side of thedie to ensure proper isolation of the die terminals.

FIG. 4 shows a vertical power diode die in which current flowsvertically through the active area 208 of the die between the (top)anode terminal and the (bottom) cathode terminal of the diode. Similarto the vertical transistor configuration shown in FIG. 2, an insulator210 such as a dielectric or molding compound covering the bottom side ofthe cathode terminal or a pn junction ensures proper electricalisolation between the cathode terminal of the die and the uppermostmetal layer of the package substrate. The cathode terminal is brought upto the front side of the die so that all electrical connections are madeat this side of the die. A termination/passivation layer 211 is providedat the front side of the die to ensure proper isolation of the dieterminals.

FIG. 5 shows a vertical power diode die similar to the one shown in FIG.4, however, the position of the anode and cathode terminals are switchedso that the cathode terminal is at the front side of the die and theanode terminal is at the backside. An insulator 210 such as a dielectricor molding compound covering the bottom side of the anode terminal or apn junction ensures proper electrical isolation between the anodeterminal of the die and the uppermost metal layer of the packagesubstrate. The anode terminal is brought up to the front side of the dieso that all electrical connections are made at this side of the die.

FIG. 6 shows a vertical transistor die similar to the one shown in FIG.2, however, the drain/collector terminal is not brought up to the frontside of the die. Instead, the drain/collector terminal is contacted atthe side of the die and remains isolated from the underlying packagesubstrate by the insulator/pn junction structure 202 formed on thebackside of the die.

FIG. 7 shows a vertical diode die similar to the one shown in FIG. 4,however, the cathode terminal is not brought up to the front side of thedie. Instead, the cathode terminal is contacted at the side of the dieand remains isolated from the underlying package substrate by theinsulator/pn junction structure 210 formed on the backside of the die.

FIG. 8 shows a vertical transistor die similar to the one shown in FIG.2, however, the drain/collector terminal is brought up to the front sideof the die along at least two sides of the vertical active area.

FIG. 9 shows a vertical diode die similar to the one shown in FIG. 4,however, the cathode terminal is brought up to the front side of the diealong at least two sides of the vertical active area.

FIG. 10 illustrates a sectional view of another embodiment of a powersemiconductor package. The power semiconductor package comprises asubstrate 300 and two groups 302, 304 of power semiconductor dies eachhaving a backside attached to the substrate 300, the backside of eachdie being insulated or isolated from the substrate 300 e.g. aspreviously described herein with respect to FIGS. 2-9.

The substrate 300 includes a lowermost metal layer 306, an uppermostmetal layer 308, and at least a first insulating layer 310 separatingthe lowermost metal layer 306 from the uppermost metal layer 308. Theuppermost metal layer 308 is patterned into a plurality of strips 308 a,308 b which extend in parallel over a width of the substrate 300. Afirst group 302 of the semiconductor dies is attached to a first one ofthe strips 308 a of the uppermost metal layer 308 and evenly distributedover the width of the first strip 308 a. A second group 304 of thesemiconductor dies is attached to the same strip 308 a of the uppermostmetal layer 308 as the first group 302 of dies, and is evenlydistributed over the width of the strip 308 a. Each semiconductor die inthe first and second groups 302, 304 has an insulated or isolated faceattached to the first strip 308 a e.g. as previously described hereinwith respect to FIGS. 2-9. The first group 302 of semiconductor dies iselectrically connected in series to the second group 304 ofsemiconductor dies to form a half bridge circuit.

A generic circuit schematic of an exemplary half bridge inverter isshown in FIG. 10, where device Q1 generically represents the first group302 of semiconductor dies and device Q2 generically represents thesecond group 304 of semiconductor dies. Each device Q1, Q2 shown in thecircuit schematic is implemented by a plurality of semiconductor diesattached in a row to one strip 308 a of the uppermost metal layer 308 ofthe substrate 300. The semiconductor dies can include power MOSFETs(metal-oxide-semiconductor field effect transistors), IGBTs (insulatedgate bipolar transistors, III-V power semiconductor transistors such asGaN transistors, etc. The transistor devices can be lateral or verticaldevices.

One or more additional series-connected (half bridge) groups ofsemiconductor dies can be attached to further strips (not shown) of theuppermost metal layer 308 of the substrate 300 to form a multi-phaseinverter e.g. as schematically illustrated in FIGS. 1A and 1B.Alternatively, the circuit can be a multi-level inverter as describedlater herein. In each case, a DC+ terminal is attached to the same strip308 a of the uppermost metal layer 308 as the semiconductor dies in thefirst and second groups 302, 304 and evenly distributed over the widthof the metal strip 308 a. A DC− terminal is attached to a differentstrip 308 b of the uppermost metal layer 308 than the DC+ terminal andevenly distributed over the width of that metal strip 308 b. Evenlydistributing the semiconductor dies and the DC terminals across thewidth of the substrate 300 ensures a relatively even spread of currentflowing through the parallel plate waveguide structure.

According to the embodiment shown in FIG. 10, the bottom plate of thewaveguide structure is formed by the uppermost metal layer 308 of thesubstrate 300. The top plate of the waveguide approximates a planarplate design and is formed by bond wire connections 312 to the top metallayer 308 of the substrate 300 and to the power semiconductor dies inthe first and second groups 302, 304, and the power semiconductor diesthemselves. Current enters the uppermost metal layer 308 of thesubstrate 300 via the DC+ terminal of the package which is attached tothe same strip 308 b of the uppermost metal layer 308 as the in thefirst and second groups 302, 304 of semiconductor dies. Current exitsthrough the approximated upper plate via the DC− terminal. Unlike theembodiment illustrated in FIGS. 1A and 1B, conductive via connections tointermediary metal layers of the substrate 300 are not needed due to theuse of semiconductor dies having an insulated or isolated backside, thussimplifying the substrate design and reducing the number of disturbancesin the lower plate of the waveguide structure.

The drain (collector) terminal of the semiconductor dies in the firstgroup 302 are electrically connected to the same strip 308 b of theuppermost metal layer 308 as the DC+ terminal, through a plurality ofcorresponding bond wire connections 312. The source (emitter) terminalof the semiconductor dies in the first group 302 are electricallyconnected to an additional metal strip 314 separated from the uppermostmetal layer 308 of the substrate 300 by an insulating layer 316, througha plurality of corresponding bond wire connections 312. The drain(collector) terminal of the semiconductor dies in the second group 304are electrically connected to the additional metal strip 314 insulatedfrom the uppermost metal layer 308 of the substrate 300, throughcorresponding bond wire connections 312. The source (emitter) terminalof the semiconductor dies in the second group 304 are electricallyconnected to the same strip 308 b of the uppermost metal layer 308 asthe DC− terminal, through corresponding bond wire connections 312. TheAC terminal of the power semiconductor package is attached to theadditional metal strip 314 insulated from the uppermost metal layer 308of the substrate 300.

FIGS. 11 through 14 illustrate additional embodiments of powersemiconductor packages having a parallel plate waveguide structure andwith a pluggable or press-fit type interface.

FIG. 11 illustrates an embodiment of a power semiconductor package thatcomprises a substrate having a lowermost metal layer 400, an uppermostmetal layer 402 and an intermediary metal layer 404 insulated from theuppermost and lowermost metal layers 400, 402 by respective insulatinglayers 406, 408. A first group 410 of semiconductor dies is attached tothe bottom side of the intermediary metal layer 404 and evenlydistributed over a width of the intermediary metal layer 404. Eachsemiconductor die in the first group 410 has an insulated or isolatedface attached to the bottom side of the intermediary metal layer 404e.g. as previously described herein with respect to FIGS. 2-9. A secondgroup 412 of semiconductor dies is attached to the top side of theintermediary metal layer 404 and evenly distributed over the width ofthe intermediary metal layer 404. Each semiconductor die in the secondgroup 412 has an insulated or isolated face attached to the second sideof the intermediary metal layer 404 e.g. as previously described hereinwith respect to FIGS. 2-9. The first group 410 of semiconductor dies iselectrically connected in series to the second group 412 ofsemiconductor dies to form a half bridge circuit.

A generic circuit schematic of an exemplary half bridge circuit is shownin FIG. 11, where device Q1 generically represents the first group 410of semiconductor dies and device Q2 generically represents the secondgroup 412 of semiconductor dies. Each device Q1, Q2 shown in the circuitschematic is implemented by a plurality of semiconductor dies attachedin a row to the intermediary metal layer 404 of the substrate. Thesemiconductor dies can include power MOSFETs (metal-oxide-semiconductorfield effect transistors), IGBTs (insulated gate bipolar transistors,III-V power semiconductor transistors such as GaN transistors, etc. Thetransistor devices can be lateral or vertical devices.

One or more additional series-connected (half bridge) groups ofsemiconductor dies can be attached to further strips (not shown) of theintermediary metal layer 404 of the substrate to form a multi-phaseinverter. Alternatively, the circuit can be a multi-level inverter asdescribed later herein. In each case, the lowermost metal layer 400 ofthe substrate forms the DC+ terminal of the power semiconductor packageand the uppermost metal layer 402 of the substrate forms the DC−terminal of the power semiconductor package. The position of the DC+ andDC− terminals can be reversed, to yield an alternative design with thesame parallel plate waveguide features. In either case, the intermediarymetal layer 404 of the substrate forms the AC terminal of the powersemiconductor package. The AC and DC terminals are each evenlydistributed over the width of the substrate, to ensure a relatively evenspread of current flowing through the parallel plate waveguidestructure.

The intermediary metal layer 404 of the substrate, which forms the ACterminal of the half bridge circuit, is partly shielded by the DC+ andDC− terminals and forms part of a 3-layer parallel plate designaccording to this embodiment. The middle plate of the waveguide isformed by the intermediary metal layer 404 of the substrate, the lowerplate of the waveguide is formed by the lowermost metal layer 400 of thesubstrate and the upper plate of the waveguide is formed by theuppermost metal layer 402 of the substrate. If the metal layers 400,402, 404 of the substrate are spaced close enough and the insulatinglayers 406, 408 of the substrate are not too thick, low parasiticinductance is realized between the metal layers 400, 402, 404.

An insulating material 414 such as a plastic molding compound canencapsulate the first and second groups 410, 412 of semiconductor dies,part of the uppermost metal layer 402, part of the lowermost metal layer400, and part of the intermediary metal layer 404 so that the uppermostmetal layer 402, the lowermost metal layer 400 and the intermediarymetal layer 404 protrude from the insulating material 414. The end ofthe substrate that protrudes from the insulating material 414 can form apluggable or press-fit type interface with a correspondingly-shapedconnector 416 having metal layers 418 separated by insulating layers420.

Cooling can be provided through the intermediary (AC) metal layer 404 ofthe substrate by integrated channels for liquid or attached heat sinks.For example, as illustrated in FIG. 11, the intermediary metal layer 404of the substrate protrudes from opposing sides of the insulatingmaterial 414. At the exposed end of the intermediary metal layer 404opposite the pluggable/press-fit type interface, a first heatsink 422can be attached to the top side of the intermediary metal layer 404 anda second heatsink 424 can be attached to the bottom side of theintermediary metal layer 404.

FIG. 12 illustrates another embodiment of a power semiconductor packagehaving a parallel plate waveguide formed by three metal layers 400, 402,404 of a substrate. The embodiment shown in FIG. 12 is similar to theembodiment shown in FIG. 11. Different, however, cooling is providedthrough the insulating material 414 that encapsulates the semiconductordies and part of the substrate. A first heatsink 500 can be attached toa first (bottom) side of the insulating material 414 covering the firstgroup 410 of semiconductor dies. A second heatsink 502 can be attachedto a second (top) side of the insulating material 414 covering thesecond group 412 of semiconductor dies.

Further according to the embodiment illustrated in FIG. 12,metallization 504 is formed on the insulated/isolated semiconductor diesto provide electrical connections to the DC+, DC− and AC terminalsrealized by the metal layers 400, 402, 404 of the substrate. Themetallization 504 can be deposited e.g. by sputtering, electroplating(galvanic deposition), etc. In one embodiment, a chip embeddingtechnology such as eWLB (embedded wafer level ball grid array) can beused to form the metal and insulating layers 404-408 of the substrateand the metallization 504 that provides electrical connections to theDC+, DC− and AC terminals realized by the metal layers 400, 402, 404 ofthe substrate.

FIG. 13 illustrates yet another embodiment of a power semiconductorpackage having a parallel plate waveguide formed by three metal layers400, 402, 404 of a substrate. The embodiment shown in FIG. 13 is similarto the embodiment shown in FIG. 11. Different, however, the end of theintermediary metal layer 404 closest to the pluggable/press-fit typeinterface is covered by an insulating material 506 and therefore notexposed. Electrical contact to the intermediary metal layer 404 of thesubstrate is made at the opposite end.

FIG. 14 illustrates still another embodiment of a power semiconductorpackage having a parallel plate waveguide formed by three metal layers400, 402, 404 of a substrate. The embodiment shown in FIG. 14 is similarto the embodiment shown in FIG. 13. Different, however, the intermediarymetal layer 404 terminates at the end closest to the pluggable/press-fittype interface prior to extending between the uppermost and lowermostmetal layers 400, 402 of the substrate. This way, the uppermost andlowermost metal layers 400, 402 are separated from one another by only asingle insulating layer 406.

FIG. 15 illustrates an embodiment of a power semiconductor package thatcomprises a substrate 600 such as a PCB, laminate or substrate formed bya chip embedding technology such as eWLB. The substrate 600 has aplurality of metal layers 602, 604, 606, 608 separated from one anotherby respective insulating layers 610, 612, 614. The parallel platewaveguide is formed by the metal layers 602, 604, 606, 608 of thesubstrate 600. Conductive vias 616 within the substrate interconnect theparallel plates.

A first group 618 of semiconductor dies is attached to a first side ofthe substrate 600 and evenly distributed over a width of the substrate600. Each semiconductor die in the first group 618 has all terminals atone side which is attached to the first side of the substrate 600 and aninsulated or isolated face at the opposite side e.g. as previouslydescribed herein with respect to FIGS. 2-9. A second group 620 ofsemiconductor dies is attached to a second side of the substrate 600opposite the first side and evenly distributed over the width of thesubstrate 600. Each semiconductor die in the second group 620 has allterminals at one side which is attached to the second side of thesubstrate 600 and an insulated or isolated face at the opposite sidee.g. as previously described herein with respect to FIGS. 2-9. The firstgroup 618 of semiconductor dies is electrically connected in series tothe second group 620 of semiconductor dies to form a half bridgecircuit.

A generic circuit schematic of an exemplary half bridge circuit is shownin FIG. 15, where device Q1 generically represents the first group 618of semiconductor dies and device Q2 generically represents the secondgroup 620 of semiconductor dies. Each device Q1, Q2 shown in the circuitschematic is implemented by a plurality of semiconductor dies attachedin a row to one strip of either the uppermost or lowermost metal layer602/604 of the substrate 600. The semiconductor dies can include powerMOSFETs (metal-oxide-semiconductor field effect transistors), IGBTs(insulated gate bipolar transistors, III-V power semiconductortransistors such as GaN transistors, etc. The transistor devices can belateral or vertical devices.

One or more additional series-connected (half bridge) groups ofsemiconductor dies can be attached to further strips (not shown) of theuppermost and lowermost metal layers 602, 604 of the substrate 604 toform a multi-phase inverter. Alternatively, the circuit can be amulti-level inverter as described later herein. In each case, thelowermost metal layer 602 of the substrate 600 is patterned to form boththe DC+ plane of the power semiconductor package and a pathway forcarrying gate signals to the semiconductor dies in the first group 618of dies. The uppermost metal layer 604 of the substrate 600 is patternedto form both the DC− plane of the power semiconductor package and apathway for carrying gate signals to the semiconductor dies in thesecond group 620 of dies. The position of the DC+ and DC− planes withinthe substrate 600 can be reversed, to yield an alternative design withthe same parallel plate waveguide features. In either case, the AC andDC planes are each evenly distributed over the width of the substrate600 to ensure a relatively even spread of current flowing through theparallel plate waveguide structure.

Further according to the embodiment illustrated in FIG. 15, a firstheatsink 622 can be attached to the insulated or isolated face of eachsemiconductor die included in the first group 618 of dies. Similarly, asecond heatsink 624 can be attached to the insulated or isolated face ofeach semiconductor die included in the second group 620 of dies.

FIG. 16 illustrates an embodiment of a power semiconductor package thatcomprises a substrate 700 having a lowermost metal layer 702, anuppermost metal layer 704, and an intermediary metal layer 706 separatedfrom the lowermost metal layer 702 by a first insulating layer 708 andseparated from the uppermost metal layer 704 by a second insulatinglayer 710. The uppermost metal layer 704 is patterned into a pluralityof strips 704 a-704 g which extend in parallel over the width of thesubstrate 700.

A first group 712 of semiconductor dies is attached to a first one ofthe strips 704 a of the uppermost metal layer 704 and evenly distributedover the width of the first strip 704 a. Each semiconductor die in thefirst group 712 has an insulated or isolated face attached to the firststrip 704 a e.g. as previously described herein with respect to FIGS.2-9. A second group 714 of semiconductor dies is attached to the samefirst metal strip 704 a as the first group 712 of dies and also evenlydistributed over the width of the first strip 704 a. Each semiconductordie in the second group 714 has an insulated or isolated face attachedto the first strip 704 a e.g. as previously described herein withrespect to FIGS. 2-9.

A third group 716 of semiconductor dies is attached to a second one ofthe strips 704 b of the uppermost metal layer 704 and evenly distributedover the width of the second strip 704 b. Each semiconductor die in thethird group 716 has an insulated or isolated face attached to the secondstrip 704 b e.g. as previously described herein with respect to FIGS.2-9. A fourth group 718 of semiconductor dies is attached to the samesecond metal strip 704 b as the third group 716 of dies and also evenlydistributed over the width of the second strip 704 b. Each semiconductordie in the fourth group 718 has an insulated or isolated face attachedto the second strip 704 b e.g. as previously described herein withrespect to FIGS. 2-9.

A fifth group 720 of semiconductor dies is attached to a third one ofthe strips 704 c of the uppermost metal layer 704 and evenly distributedover the width of the third strip 704 c. Each semiconductor die in thefifth group 720 has an insulated or isolated face attached to the thirdstrip 704 c e.g. as previously described herein with respect to FIGS.2-9. A sixth group 722 of semiconductor dies is attached to the samethird metal strip 704 c as the fifth group 720 of dies and also evenlydistributed over the width of the third strip 704 c. Each semiconductordie in the sixth group 722 has an insulated or isolated face attached tothe third strip 704 c e.g. as previously described herein with respectto FIGS. 2-9.

The first group 712 of semiconductor dies is electrically connected inseries to the second group 714 of semiconductor dies, the third group716 of semiconductor dies is electrically connected in series to thefourth group 718 of semiconductor dies, and the fifth group 720 ofsemiconductor dies is electrically connected in series to the sixthgroup 722 of semiconductor dies to form a 3-phase inverter. A genericcircuit schematic of an exemplary 3-phase inverter is shown in FIG. 16,where device Q1 generically represents the first group 712 ofsemiconductor dies, device Q2 generically represents the second group714 of semiconductor dies, etc. Each device Q1, Q2, . . . , Q6 shown inthe circuit schematic is implemented by a plurality of semiconductordies attached in a row to one strip of the uppermost metal layer 704 ofthe substrate 700. The semiconductor dies can include power MOSFETs(metal-oxide-semiconductor field effect transistors), IGBTs (insulatedgate bipolar transistors, III-V power semiconductor transistors such asGaN transistors, etc. The transistor devices can be lateral or verticaldevices.

To ensure current sharing of paralleled power semiconductors, each groupof semiconductor dies is evenly distributed in a row over the width ofthe metal strip to which those dies are attached. The direction of eachrow of dies is oriented perpendicular to the current flowing within theparallel plates of the waveguide structure. The parallel plate waveguidestructure comprises the uppermost metal layer 704 and the intermediarymetal layer 706 of the substrate 700. Current enters the intermediarymetal layer 706 via the DC+ terminal of the package which is attached toone of the strips 704 g of the uppermost metal layer 704, and currentexits through the uppermost metal layer 704 via the DC− terminal. TheDC+ and DC− terminals are evenly distributed over the width of thecorresponding metal strips 704 c, 704 g to ensure the current is spreadrelatively evenly across the width of the substrate 700. Electricalconnections from the drains of the high side transistors represented bydevices Q1, Q3 and Q5 in the circuit schematic to the intermediary metallayer 706 of the substrate 700 which forms the DC+ plane are provided byconductive vias 724 which extend through and are insulated from theuppermost metal layer 704 of the substrate 700 and through the upperinsulating layer 710 of the substrate 700. The position of the DC+ andDC− planes within the substrate 700 can be reversed, to yield analternative design with the same parallel plate waveguide features. Ineither case, the DC terminals are each evenly distributed over the widthof the substrate 700 to ensure a relatively even spread of currentflowing through the parallel plate waveguide structure.

The AC terminals of the 3-phase inverter are provided above thesubstrate 700. More particularly, a first AC terminal AC1 is attached toa first additional metal strip 726 disposed over the first strip 704 aof the uppermost metal layer 704 of the substrate. The first additionalmetal strip 726 is disposed between the first and second groups 712, 714of semiconductor dies, extends over the width of the first strip 704 a,and is separated from the uppermost metal layer 704 by an insulatinglayer 728. The first AC terminal AC1 is evenly distributed over thewidth of the first additional metal strip 726. A second AC terminal AC2is attached to a second additional metal strip 730 disposed over thesecond strip 704 b of the uppermost metal layer 704 of the substrate700. The second additional metal strip is disposed between the third andfourth groups 716, 718 of semiconductor dies, extends over the width ofthe second strip 704 b, and is separated from the uppermost metal layer704 by an insulating layer 732. The second AC terminal AC2 is evenlydistributed over the width of the second additional metal strip 730. Athird AC terminal AC3 is attached to a third additional metal strip 734disposed over the third strip 704 c of the uppermost metal layer 704 ofthe substrate 700. The third additional metal strip 734 is disposedbetween the fifth and sixth groups 720, 722 of semiconductor dies,extends over the width of the third strip 704 c, and is separated fromthe uppermost metal layer 704 by an insulating layer 736. The third ACterminal AC3 is evenly distributed over the width of the thirdadditional metal strip 734. Each AC terminal can be implemented as aseparate busbar or as a plurality of pins attached in a row anddistributed evenly over the width of the corresponding additional metalstrip disposed above the substrate 700.

The embodiment illustrated in FIG. 16 expands the parallel platewaveguide design illustrated in FIG. 10 (half bridge inverter) toaccommodate a 3-level topology. Compared to the embodiment illustratedin FIGS. 1A and 1B, the embodiment illustrated in 16 requires one lessinsulation layer in the substrate 700 to realize the parallel platewaveguide. The additional insulation layer is omitted due to the use ofsemiconductor dies having an insulated or isolated face attached to theuppermost metal layer 704 of the substrate 700.

FIG. 17 illustrates an embodiment of a power semiconductor package whichis similar to the embodiment shown in FIG. 15. Different, however, thecircuit is expanded from a single half bridge inverter to a 3-phaseinverter as indicated by the equivalent circuit schematic shown in FIG.17. Each pair of series-connected groups of semiconductor dies isrepresented by one leg Q1/Q2, Q3/Q4, Q5/Q6 of the 3-phase circuitschematic in FIG. 17. Each device Q1, Q2, etc. is implemented by aplurality of semiconductor dies attached in a row to a correspondingstrip of the lowermost metal layer 802 of the substrate 800, aspreviously described herein in connection with FIG. 15. Also differentfrom the embodiment of FIG. 15, all of the semiconductor dies areattached at their respective insulated/isolated side to the same side ofthe substrate 800. The design of the substrate 800 is altered to bringall electrical connections out at the opposite side of the substrate 800i.e. the side opposite the dies. Also, a first intermediary metal layer804 of the substrate 804 forms the DC+ plane of the power semiconductorpackage and a second intermediary metal layer 806 of the substrate 800forms the DC− plane of the power semiconductor package. The intermediarymetal layers 804, 806 of the substrate 800 are insulated from oneanother and form the parallel plate waveguide. The same heatsink 808 canbe attached to the insulated or isolated face of each semiconductor die,which faces away from the substrate 800 in this embodiment.

FIG. 18 illustrates an embodiment of a power semiconductor package whichis similar to the embodiments shown in FIGS. 10 and 16. Different,however, is the circuit implemented. Instead of a single half bridge or3-phase inverter, the package implements the 3-level converterschematically illustrated in FIG. 18. The 3-level converter has threeinput and output paths, depending on the controllable commutation pathsimplemented between the switches and diodes. This way, the AC terminalcan be coupled to DC+, DC− or a midpoint level ‘N’. The midpoint level‘N’ is realized between two capacitors C1, C2 connected in seriesbetween the DC+ and DC− terminals. A first pair of series-connecteddevices Q1/Q2 provides a controllable path between midpoint level ‘N’and the AC terminal. A second pair of series-connected devices Q3/Q4provides a controllable path between either DC+ or DC− and the ACterminal. Each device Q1, Q2, Q3, Q4 shown in the circuit schematic isimplemented by a plurality of semiconductor dies attached in a row toone strip 902 a/902 b of the uppermost metal layer 902 of the substrate900. The semiconductor dies can include power MOSFETs(metal-oxide-semiconductor field effect transistors), IGBTs (insulatedgate bipolar transistors, III-V power semiconductor transistors such asGaN transistors, etc. The transistor devices can be lateral or verticaldevices.

The semiconductor dies that form device Q1 are attached to a first strip902 a of the uppermost metal layer 902 of the substrate 900 and evenlydistributed over the width of the first strip 902 a. The semiconductordies that form device Q2 are attached to the same first metal strip 902a as the semiconductor dies that form device Q1, and are evenlydistributed over the width of the first strip 902 a. Each semiconductordie that forms device Q1 and each semiconductor die that forms device Q2has an insulated or isolated face attached to the first metal strip 902a e.g. as previously described herein with respect to FIGS. 2-9. Thesemiconductor dies that form device Q1 are electrically connected inseries to the semiconductor dies that form device Q2, as illustrated inthe corresponding circuit schematic.

The semiconductor dies that form device Q3 are attached to a secondstrip 902 b of the uppermost metal layer 902 of the substrate 900 andevenly distributed over the width of the second strip 902 b. Thesemiconductor dies that form device Q4 are attached to the same secondmetal strip 902 b as the semiconductor dies that form device Q3, and areevenly distributed over the width of the second strip 902 b. Eachsemiconductor die that forms device Q1 and each semiconductor die thatforms device Q2 has an insulated or isolated face attached to the secondmetal strip 902 b e.g. as previously described herein with respect toFIGS. 2-9. The semiconductor dies that form device Q1 are electricallyconnected in series to the semiconductor dies that form device Q2, asillustrated in the corresponding circuit schematic.

The terminal for the midpoint level ‘N’ of the 3-level converter circuitis provided above the substrate 900 according to the embodimentillustrated in FIG. 18. More particularly, the terminal for the midpointlevel ‘N’ is attached to an additional metal strip 906 disposed over andinsulated from the first strip 902 a of the uppermost metal layer 902 ofthe substrate 900. The additional metal strip 906 is disposed betweencapacitor C2 and the semiconductor dies that form device Q1, extendsover the width of the first strip 902 a, and is separated from thesubstrate 900 by an insulating layer 908. The parallel plate waveguideis formed by the uppermost metal layer 902 and intermediary metal layer910 of the substrate 900 according to this embodiment.

FIG. 19 illustrates an embodiment of a power semiconductor package whichis similar to the embodiment shown in FIG. 18. Different, however, theterminal for the midpoint level ‘N’ of the 3-level converter circuit isattached to the top terminal of capacitor C1.

As used herein, the terms “having”, “containing”, “including”,“comprising” and the like are open ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

It is to be understood that the features of the various embodimentsdescribed herein may be combined with each other, unless specificallynoted otherwise.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A power semiconductor package, comprising: asubstrate comprising a lowermost metal layer, an uppermost metal layer,and an intermediary metal layer separated from the lowermost metal layerby a first insulating layer and separated from the uppermost metal layerby a second insulating layer, the uppermost metal layer being patternedinto a plurality of strips which extend in parallel over a width of thesubstrate; a first group of semiconductor dies attached to a first oneof the strips of the uppermost metal layer and evenly distributed overthe width of the first strip, each semiconductor die in the first grouphaving an insulated or isolated face attached to the first strip; asecond group of semiconductor dies attached to the first strip of theuppermost metal layer and evenly distributed over the width of the firststrip, each semiconductor die in the second group having an insulated orisolated face attached to the first strip; a third group ofsemiconductor dies attached to a second one of the strips of theuppermost metal layer and evenly distributed over the width of thesecond strip, each semiconductor die in the third group having aninsulated or isolated face attached to the second strip; and a fourthgroup of semiconductor dies attached to the second strip of theuppermost metal layer and evenly distributed over the width of thesecond strip, each semiconductor die in the fourth group having aninsulated or isolated face attached to the second strip, wherein thefirst group of semiconductor dies is electrically connected in series tothe second group of semiconductor dies, wherein the third group ofsemiconductor dies is electrically connected in series to the fourthgroup of semiconductor dies.
 2. The power semiconductor package of claim1, further comprising: a fifth group of semiconductor dies attached to athird one of the strips of the uppermost metal layer and evenlydistributed over the width of the third strip, each semiconductor die inthe fourth group having an insulated or isolated face attached to thethird strip; a sixth group of semiconductor dies attached to the thirdstrip of the uppermost metal layer and evenly distributed over the widthof the third strip, each semiconductor die in the fourth group having aninsulated or isolated face attached to the third strip; a first DCterminal attached to the third strip of the uppermost metal layer andevenly distributed over the width of the third strip; and a second DCterminal attached to a fourth one of the strips of the uppermost metallayer and evenly distributed over the width of the fourth strip, whereinthe fifth group of semiconductor dies is electrically connected inseries to the sixth group of semiconductor dies.
 3. The powersemiconductor package of claim 2, further comprising: a first ACterminal attached to a first additional metal strip disposed over andinsulated from the first strip of the uppermost metal layer of thesubstrate, the first additional metal strip being disposed between thefirst and the second groups of semiconductor dies and extending over awidth of the first strip, the first AC terminal being evenly distributedover the width of the first additional metal strip; a second AC terminalattached to a second additional metal strip disposed over and insulatedfrom the second strip of the uppermost metal layer of the substrate, thesecond additional metal strip being disposed between the third and thefourth groups of semiconductor dies and extending over a width of thesecond strip, the second AC terminal being evenly distributed over thewidth of the second additional metal strip; and a third AC terminalattached to a third additional metal strip disposed over and insulatedfrom the third strip of the uppermost metal layer of the substrate, thethird additional metal strip being disposed between the fifth and thesixth groups of semiconductor dies and extending over a width of thethird strip, the third AC terminal being evenly distributed over thewidth of the third additional metal strip.
 4. The power semiconductorpackage of claim 1, wherein at least one of the first, second, third andfourth groups of semiconductor dies includes a plurality of verticalpower transistor die in which current flows vertically through an activearea of each vertical power transistor die between a source/emitterterminal and a drain/collector terminal of the vertical power transistordie, wherein the amount of current flow is controlled by a voltageapplied to a gate terminal which is disposed at a front side of thevertical power transistor die, wherein the source/emitter terminal isdisposed at the front side, wherein the drain/collector terminal isdisposed at a backside of the active area, wherein an insulator coveringa bottom side of the drain/collector terminal or a pn junction provideselectrical isolation between the drain/collector terminal of the die andthe uppermost metal layer of the package substrate.
 5. The powersemiconductor package of claim 4, wherein the drain/collector terminalof each vertical power transistor die is brought up to the front side ofthe die so that all electrical connections to the vertical powertransistor die are made at the front side.
 6. The power semiconductorpackage of claim 5, wherein the drain/collector terminal of eachvertical power transistor die is brought up to the front side of thevertical power transistor die along at least two sides of the activearea.
 7. The power semiconductor package of claim 5, wherein apassivation layer at the front side of each vertical power transistordie isolates the terminals at the front side.
 8. The power semiconductorpackage of claim 4, wherein the drain/collector terminal of eachvertical power transistor die is contacted at a side of the active area.9. The power semiconductor package of claim 1, wherein at least one ofthe first, second, third and fourth groups of semiconductor diesincludes a plurality of lateral power transistor dies in which currentflows laterally through an active area of each lateral power transistordie between a source/emitter terminal and a drain/collector terminal ofthe lateral power transistor die, wherein each terminal of the lateralpower transistor die is formed at a front side of the lateral powertransistor die which faces away from the substrate, and wherein aninsulator covering a bottom side of the active area or a pn junctionprovides electrical isolation between the lateral power transistor dieand the uppermost metal layer of the package substrate.
 10. The powersemiconductor package of claim 9, wherein a passivation layer at thefront side of each die lateral power transistor isolates the terminalsat the front side.
 11. The power semiconductor package of claim 1,wherein at least one of the first, second, third and fourth groups ofsemiconductor dies includes a plurality of vertical power diode dies inwhich current flows vertically through an active area of each verticalpower diode die between an anode terminal and a cathode terminal of thevertical power diode die, wherein an insulator covering a bottom side ofthe cathode terminal or a pn junction provides electrical isolationbetween the cathode terminal of the vertical power diode die and theuppermost metal layer of the package substrate.
 12. The powersemiconductor package of claim 11, wherein the cathode terminal of eachvertical power diode die is brought up to a front side of the verticalpower diode die so that all electrical connections to the vertical powerdiode die are made at the front side.
 13. The power semiconductorpackage of claim 12, wherein the cathode terminal of each vertical powerdiode die is brought up to the front side of the vertical power diodedie along at least two sides of the active area.
 14. The powersemiconductor package of claim 12, wherein a passivation layer at thefront side of each vertical power diode die isolates the terminals atthe front side.
 15. The power semiconductor package of claim 11, whereinthe cathode terminal of each vertical power diode die is contacted at aside of the active area.
 16. The power semiconductor package of claim 1,wherein at least one of the first, second, third and fourth groups ofsemiconductor dies includes a plurality of vertical power diode dies inwhich current flows vertically through an active area of each verticalpower diode die between an anode terminal and a cathode terminal of thevertical power diode die, wherein an insulator covering a bottom side ofthe anode terminal or a pn junction provides electrical isolationbetween the anode terminal of the vertical power diode die and theuppermost metal layer of the package substrate.
 17. The powersemiconductor package of claim 16, wherein the anode terminal of eachvertical power diode die is brought up to a front side of the verticalpower diode die so that all electrical connections to the vertical powerdiode die are made at the front side.
 18. The power semiconductorpackage of claim 16, wherein a passivation layer at a front side of eachvertical power diode die isolates the terminals at the front side.